1. Field of the Invention
The present invention relates to an information processing apparatus for performing scaling processing on image data.
2. Description of the Related Art
Known processing methods for creating print data from electronic documents include print instructions using a page description language (PDL).
In other words, a printer driver operating on a host computer converts print instructions from application software into PDL print data that can be processed by image processing apparatuses.
An image processing apparatus that receives a print processing job is configured to create a bitmap image (page image) representing the content of a page corresponding to the PDL.
Such image data rendering commands in PDL includes a group of commands such as character printing commands, various graphic commands including line drawing commands, and image rendering commands.
Some of the image data rendering commands in PDL include versatile commands such as logical rendering operations (specifying a raster operation (ROP) such as AND or OR), specifying a clipping area, macro commands storing and calling a plurality of commands in a group, and a command group for setting up various printing environments.
In accordance with the development of a print on demand (POD) market and increasingly versatile user needs in recent years, the content of print instructions from application software such as DTP or CAD software, output to image processing apparatuses such as page printers, is becoming increasingly complex.
Hence, there is an increasing demand for an increased processing speed for PDL data.
Examples of the cases in which the content of printing commands becomes complex, as described above, or the volume of the commands increases include cases in which image data handled by application software is divided into a plurality of minute areas, and is rendered as a large number of fragmentary pieces of image data.
In some of these cases, application software divides a single block of image data into around a million minute areas, in accordance with the kind of the application, the size of the original image data, or the printing resolution with which an image processing apparatus processes the data.
In this case, when reduction is specified for the individual divided image data blocks in accordance with print settings or the kind of applications, the printing performance is decreased due to the following reasons.
(1) The size of print data is too large since image data before reduction, which exceeds the size of a print area printed by an image processing apparatus, is sent from a printer driver to the image processing apparatus.
(2) A reduction process for received image data is required in the image processing apparatus to suppress the degradation of quality in accordance with the reduction ratio specified by the printer driver, using a predetermined interpolation algorithm.
In a great number of cases, an individual divided minute image data block is a single-color image data block which consists of pixels having the same color value.
As a technology for increasing the processing speed for such single-color images, the following technology is disclosed in Japanese Patent Laid-Open No. 2000-255123.
(1) It is determined whether or not image data consists of a single color, and when it is determined that the image data consists of a single color, a color conversion process for part of the image data is omitted, and the area for which the process was omitted uses the same color value as that of the result of the color conversion process for other parts, thereby increasing the speed of the color conversion process.
(2) It is determined whether or not image data can be converted into graphic data, and the image data that has been determined to be able to be converted into graphic data is converted into graphic data.
The following technology is disclosed in Japanese Patent Laid-Open No. 2001-101431 as a technology for increasing the speed using the characteristic of the pixels of a rendering object.
(1) By detecting the horizontal or vertical direction of gradation, a portion of the image in a direction perpendicular to the gradation direction is replaced with a number of adjacent pixels having the gradation level of the first pixel (a line of pixels having the same gradation is created by copying the first pixel).
(2) Gradation is created by repeatedly copying the pixels of the first row for the horizontal gradation and repeatedly copying the pixels of the first column for the vertical gradation.
In the image processing apparatus described in Japanese Patent Laid-Open No. 2000-255123, input PDL commands are analyzed one by one, and image rendering commands are sequentially processed, thereby increasing the processing efficiency in the image processing apparatus.
However, Japanese Patent Laid-Open No. 2000-255123 does not address the problem that the excessive size of the print data is sent when a printer driver sends a large number of minute image data blocks to an image processing apparatus, where a reduction process is performed.
Japanese Patent Laid-Open No. 2001-101431 has a problem in that since a constant-gradation direction, i.e., a direction in which the same color value is repeated, is detected independent of the sizes of objects, a time-consuming process of detecting single-color image data for all the objects is required, thereby increasing the total processing time.
As described above, known information processing apparatuses have the problem of the excessive size of the print data and increased processing time when image data divided into minute data blocks is reduced and sent from a printer driver to an image processing apparatus to be output.